Poisoning approach and drug overdoses

Methanol and other toxic alcohols

Reviewed Nov 2026·2 references
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Suspect methanol in hooch clusters, use osmolal and anion gaps, block alcohol dehydrogenase (fomepizole or ethanol), give folinic acid, correct acidosis and dialyse early.

Definition
Methanol (illicit liquor, solvents) and ethylene glycol (antifreeze) are metabolised by alcohol dehydrogenase to toxic acids (formic acid; glycolate/oxalate), causing high anion gap metabolic acidosis, blindness (methanol), AKI (ethylene glycol) and death.

At the bedside

  1. 1

    Suspect

    Clusters after drinking illicit liquor, visual blurring ('snowfield'), abdominal pain, Kussmaul breathing; may follow a latent period of 12-24 h.

  2. 2

    Investigate

    ABG (HAGMA), anion gap, measured osmolality (osmolal gap > 10-20 suggests toxic alcohol early), ethanol level, methanol level if available, creatinine, lactate; CT head (putaminal necrosis).

  3. 3

    Block alcohol dehydrogenase

    Now

    Fomepizole (preferred) or ethanol when methanol > 20 mg/dL, or strong history with osmolal gap > 10 or acidosis. Ethanol target blood level 100-150 mg/dL.

  4. 4

    Correct acidosis

    Sodium bicarbonate to pH > 7.3 (reduces formate entry into CNS).

  5. 5

    Cofactors

    Methanol: folinic acid 50 mg IV q4-6h. Ethylene glycol: thiamine 100 mg and pyridoxine 50 mg IV q6h.

  6. 6

    Haemodialysis (EXTRIP)

    Coma, seizures, new visual deficit, pH ≤ 7.15, persistent acidosis, AG > 24, or high methanol level. Continue ADH blockade during and after HD (double ethanol dose or fomepizole q4h).

ADH blockade

Fomepizole

IV
Dose
15 mg/kg, then 10 mg/kg q12h × 4, then 15 mg/kg q12h
Worked example
70 kg: 1,050 mg load in 100 mL NS over 30 min; then 700 mg q12h

ADH blockade when fomepizole unavailable

Ethanol (antidote)

IV/oral
Dose
Load ~800 mg/kg, maintain 80-130 mg/kg/h; target 100-150 mg/dL
Worked example
70 kg oral: 56 g ethanol ≈ 175 mL of 40% spirit (diluted) load; maintenance 5.6-9.1 g/h ≈ 18-29 mL/h of 40% (double during HD)

Methanol

Folinic acid (or folic acid)

IV
Dose
50 mg q4-6h

Acidosis

Sodium bicarbonate 8.4%

IV
Dose
1-2 mEq/kg boluses to pH > 7.3
Red flag · call your senior now
Visual symptoms, pH < 7.15 or coma after illicit liquor: dialyse urgently - prognosis depends on time to HD.
Pitfall
A normal osmolal gap does not exclude late toxic alcohol poisoning (parent alcohol already metabolised).
Pitfall
Forgetting to increase ethanol/fomepizole dosing during haemodialysis.
Pearl
Calculated osmolality = 2 Na + glucose/18 + urea/6 (mg/dL); each 10 mg/dL ethanol adds about 2 mOsm/kg.

Calculators for this topic

Anion gap

Na⁺ − (Cl⁻ + HCO₃⁻). Correct for albumin.

Osmolal gap

Measured − calculated osmolality. Raised in toxic alcohol poisoning.

Calculated serum osmolality (Indian units)

2 × Na + glucose (mg/dL)/18 + urea (mg/dL)/6. Uses blood urea, as reported by most Indian labs.

References

  1. 1

    Barceloux DG, Bond GR, Krenzelok EP, Cooper H, Vale JA. American Academy of Clinical Toxicology practice guidelines on the treatment of methanol poisoning. J Toxicol Clin Toxicol 2002;40:415-46.

  2. 2

    Roberts DM, Yates C, Megarbane B, et al. Recommendations for the role of extracorporeal treatments in the management of acute methanol poisoning: a systematic review and consensus statement. Crit Care Med 2015;43:461-72.

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